Studying digital communication provides a window into the secret world of adolescent peer culture (Greenfield & Yan, 2006, p. 392). According to large, national surveys, 80% of online teens (12 - 17) use social networking sites (Madden et al., 2013). Youth ages 12 - 17 report sending an average of 60 text messages per day (Lenhart, 2012), and many claim that their social lives would end or be seriously impaired if they could not have access to text messaging (54% of girls and 40% of boys, CTIA, 2008). This proposed renewal of our ongoing longitudinal study, NICHD R01 HD060995, Social Aggression: Growth and Outcomes, will investigate how social aggression unfolds in digital communication and relates to psychosocial adjustment, how qualities of parent-child and child-friend relationships observed in middle childhood predict the development of social aggression online and offline through late adolescence, and how digital communication relates to adolescents' adjustment more broadly. This longitudinal study of a diverse sample examines social aggression and victimization across 10 years with multiple measures and informants, including observations of parent-child and child-friend interactions yearly from ages 10 - 13 and archives containing the content of participants' text messaging communication (for 4.5 years) and Facebook communication (for 2 years). This study offers the rare opportunity to examine relations among adolescents' offline relationships, socioemotional adjustment, and digital communication, from early through late adolescence. This application requests support for conducting state-of-the-art statistical analyses, performing additional coding of our digital communication data, investigating possible ethnic differences in social aggression and digital communication, and exploring the possibility of de-identifying the large archive so that it can be shared with other investigators. Because qualities of relationships and adjustment were assessed yearly by multiple informants, we will be able to investigate how social aggression (and victimization) and adjustment contribute to each other across the age range of middle childhood through late adolescence using autoregressive latent trajectory and growth-mixture models. Analyses using the dyadic growth curve and the one-with-many design will then examine how relationship dynamics with parents and friends in middle childhood relate to the long-term development of social aggression and victimization. To explore how other specific social processes (e.g., deviant peer talk, co-rumination, prosocial behavior, and provisions of support) in digital communication might relate to psychological adjustment, we propose to conduct additional coding of digital communication, using both Linguistic Interpretive Word Count (LIWC) software and our fine-grained microcoding systems. We will consult with an expert in data anonymization to explore possibilities for de- identifying the large archive of digital communication so that it could studid by other investigators.